This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. 119 from an application for DRY TONER OF POLYMERIZATION TYPE FOR ELECTRONIC PHOTOGRAPHY earlier filed in the Korean Industrial Property Office on the 13th of Oct. 1999 and there duly assigned Serial No. 44314/1999.
1. Field of the Invention
The present invention relates to a dry toner for electronic photography, and more particularly, to a dry toner of polymerization type in which a silica system compound is used as stabilizer for the polymerization process.
2. Description of the Related Art
In general, a dry toner is used in an electronic photography apparatus and is a material used to form an image on a recordable medium. Typically, a dry toner contains a coloring pigment, a high molecular weight resin for fixing the coloring pigment to a recordable medium, a charge control agent for controlling a charged amount of the toner and a release agent for preventing the toner fixed on the recordable medium from adhering to a fuser roll. Toner particles further include external additives to bestow functionality to or enhance physical properties of the toner. In these dry toners, it is generally necessary to freely control the size of the toner particles.
One type of dry toner is the pulverization type. A dry toner of pulverization type is formed by mixing a high molecular weight resin, a coloring pigment of carbon black, a charge control agent and a release agent, colliding the mixture with a collision plate using a strong vortex to thereby pulverize the mixture into fine particles and screening the fine pulverized particles using the vortex.
Many kinds of resins may be used in the dry toner of pulverization type, but this type of dry toner has a drawback of high manufacturing cost due to the investment costs of equipment for performing the pulverizing and screening processes. There is an additional drawback in the quality of the manufactured goods, since it is very difficult to control the size of the toner particles. Furthermore, due to the low uniformity of the particles sizes, poor picture quality results.
Another type of dry toner is the polymerization type which is synthesized by using a monomer of a common thermoplastic resin, a coloring pigment, a polymerization initiator, a charge control agent and a release agent. Differently from the dry toner of pulverization type, the particle size of the dry toner of polymerization type may be controlled depending on the polymerization conditions, that is, kinds and concentration of stabilizer, amount of polymerization initiator, speed of the stirring and time and temperature of polymerization. Among these conditions, the kind and concentration of the stabilizer are the factors generally affecting the particle size to the largest degree.
Stabilizer encircles the surface of a molecular aggregate of fine spherical shaped monomers created from the solvent during the suspension polymerization reaction and maintains the dispersion such that coagulation does not occur between these molecular aggregates. The polymerization reaction occurs within the molecular aggregate of the fine spherical shape encircled by the stabilizer.
The stabilizers are hydrophilic and they show a superior dispersion characteristic with respect to the solvent, that is, water. However, when the stabilizers are applied to the dry toner, it is difficult to remove the stabilizer from the toner particles after the polymerization reaction has been completed. In addition, the residual stabilizer degenerates the picture quality of transferred images.
Moreover, after the polymerization reaction has been completed, it is troublesome to withdraw the stabilizer from the solvent, which badly affects the environment. This may be a serious problem depending on components of the stabilizer.
As a stabilizer used in the polymerization reaction of dry toners, there is a phosphoric salt system compound or hydrophilic silica system compound. General stabilizers used for suspension polymerization reaction, for example, gelatin, methyl cellulose, polyvinyl alcohol, polymethacrylic acid are applied.
Phosphoric salt system compound, however, has a low stability and a low reproduction capability and also has a drawback in that it is difficult to separate the phosphoric salt system compound from toner particles. In addition, since phosphorous is contained in the phosphoric salt system compound, the phosphoric salt system compound acts as a source of environmental contamination.
The particle size of hydrophilic silica system stabilizer is too fine to control size of the toner particle. Also, the hydrophilic silica system stabilizer is very strongly hydrophilic, so that it is difficult to separate the hydrophilic silica system stabilizer from the toner particle after the polymerization reaction has been completed. Moreover, gelatin, methyl cellulose, polyvinyl alcohol and polymethacrylic acid are strongly hydrophilic, so that it is difficult to separate them from the toner particle after the polymerization reaction has been completed.
Examples of toners of the conventional art are seen in the following U.S. Patents.
U.S. Pat. No. 5,364,729, to Kmiecik-Lawrynowicz et al., entitled TONER AGGREGATION PROCESS, discloses a dry toner which is synthesized by forming an aggregate of monomers electrostatically. However, this patent has a drawback in that the reproduction of the dry toner as formed is substantially very low.
U.S. Pat. No. 5,925,488, to Patel et al., entitled TONER PROCESSES USING IN-SITU TRICALCIUM PHOSPATE [sic] discloses a dry toner which is synthesized by using a stabilizer of tricalcium phosphate. However, this patent has a drawback in that the stabilizer of tricalcium phosphate has a very low stability and badly affects the environment.
It is therefore an object of the present invention to provide an improved dry toner.
Another object of the present invention is to provide an improved fabrication process for a dry toner.
Yet another object of the invention is to provide an improved polymerization process in the fabrication process of dry toner for electronic photography apparatus, thereby providing a dry toner for electronic photography in which the size of the toner particles is freely controlled, uniformity in the particle size is enhanced and quality of the manufactured goods and picture quality of transferred image are very excellent.
It is another object of the present invention to provide a dry toner for electronic photography in which the separation rate of stabilizer from toner particles is very high and residual stabilizer does not affect the picture quality of a transferred image.
It is yet another object of the present invention to a dry toner for electronic photography which does not affect the environment.
According to the present invention, a dry toner is synthesized during a polymerization process by adding a stabilizer which is a silica system compound, that is, a silicon-containing compound, having both properties of hydrophobicity and hydrophilicity and having the following chemical structure formula 1:

wherein the silica system stabilizer has a three dimensional network structure due to crosslinking of the units of the compound. In this structural formula, x, y and z represent relative mole fractions of the corresponding units in the compound. R1 and R2 are independently selected from an aliphatic compound of C1 to C30, an aliphatic compound of C1 to C30 having at least one functional group (G), a heteroaliphatic compound of C1 to C30, a heteroaliphatic compound of C1 to C30 having at least one functional group (G), a cycloaliphatic compound, a cyclo aliphatic compound having at least one functional group (G), a heterocyclic aliphatic compound of C1 to C30, a heterocyclic aliphatic compound of C1 to C30 having at least one functional group (G), an aromatic compound of C1 to C30, an aromatic compound having at least one functional group (G). Here, independently selected means that R1 may be the same as R2.
Here, the functional group G is selected from amide (xe2x80x94CONHxe2x80x94), imine (xe2x80x94CHxe2x95x90Nxe2x80x94), amidino (xe2x80x94N(NH2)2), amine (xe2x80x94NRH, where R is an alkyl group), hydrazine (xe2x80x94NHNH2), hydrazone (xe2x80x94Nxe2x95x90NH), halide, hydroxy, nitro (xe2x80x94NO2), cyano (xe2x80x94CN), thiocyano (xe2x80x94SCN), thiol (xe2x80x94SH), carboxylic acid (xe2x80x94COOH), carboxylate salt (COOxe2x80x94M+, where M is an alkali metal), sulfonic (SO3H), alkali sulfonate acid(SO3xe2x80x94M+), phosphoric acid(xe2x80x94OPO3H2), alkali salt of phosphate (xe2x80x94OPO3Hxe2x80x94M+).
Preferably, the silica group stabilizer is contained by 0.1 to 2 wt % in the polymerization composition.
Preferably, the silica group stabilizer is contained by 0.1 to 0.2 wt % in the polymerization composition.
Preferably, the polymerization composition contains a general-purpose thermoplastic resin monomer and the general-purpose thermoplastic monomer is contained by 15 to 30 wt % in the polymerization composition. Many polymerization systems may be used in the present invention. Examples of thermoplastic monomers include: 1) styrene and xcex1-methylstyrene; 2) acrylic acid and methacrylic acid; 3) acrylic acid and methacrylic acid derivatives such as methyl acrylate, ethyl acrylate, propyl acrylate, 2-ethyl hexyl acrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, proply methacrylate and butyl methacrylate.
Preferably, the polymerization composition contains a solvent and the solvent is contained by 51.5 to 78.8 wt % in said polymerization composition.
Preferably, the solvent is formed by adding an acid solution or an alkaline solution of 0.1 to 10 wt % to water.
Preferably, the polymerization composition contains a coloring pigment of 5 to 10 wt %, a polymerization initiator of 0.1 to 2 wt %, a charge control agent of 1 to 4 wt %, and a wax group release agent of 0.1 to 0.5 wt %.